The present invention is related to devices for obstructing the backwash produced by power drive units for watercraft and more particularly to such devices that are mountable to the anticavitation plate of an outboard or an inboard-outboard type drive unit.
In the sport of troll fishing from a motor driven boat, it often becomes necessary to proceed at a speed that is somewhat slower than possible with the ordinary full idle RPM of the boat motor. This is often the situation with watercraft designed for transportation purposes rather than for fishing. If the motor is run at a slower RPM than is recommended by the manufacturer, it will often overheat, runs rough, or dies frequently. Some boat owners purchase smaller outboard engines attachable to their boat for the specific purpose of trolling. This is both an expensive and inefficient method of operation, as directional control of the boat is sacrificed for the lower speed. In addition, a separate engine mount bracket must be provided as well as additional controls and a portable fuel supply. It therefore becomes desirable to provide some mechanism that may be adapted to existing drive units that will enable proper trolling speeds for such craft and will further not hamper normal forward progress of the boat under ordinary operating conditions.
U.S. Pat. No. 2,787,974 to E. C. Johnson discloses a manually variable trolling plate for outboard motors. This device discloses a plate that is pivotably mounted to a bracket carried by the anticavitation plate of an outboard motor. The trolling plate is connected to an upright adjustment mechanism that projects from the plate to a handle end located behind the boat motor and above the water surface. It is this bracket that interfits with any of a series of notches provided along the length of the adjustment rod to facilitate positioning of the locking plate about its pivot axis. The locking mechanism provides means for positively locking the trolling plate against movement away from the propeller of the attached outboard motor but does not provide a positive means for locking the plate as the motor is operated in reverse. This may be evidenced by FIG. 3 of the drawings wherein the notches indicated by the numeral 60 face forwardly and are inclined upwardly with respect to the trolling plate 45 as shown in FIG. 1. Perhaps tension of spring 65 is sufficient to hold the notches in engagement with the locking plate 61 while the specific motor shown in the drawings is operated in reverse. But the power produced by modern outboard engines as well as inboard-outboard drives, would render utilization of such a locking apparatus impractical. Further, this device may be utilized only with outboard motors or in some other situation wherein the trolling plate unit may remain stationary relative to a movable driving unit.
U.S. Pat. No. 2,050,336 to R. Karasinski discloses a baffle plate for utilization with an outboard motor. The plate is pivoted to the anticavitation plate of the outboard motor and is biased by a torsion spring continuously toward a position intersecting the backwash produced by the propeller. Under a full throttle condition, the backwash produces sufficient force to pivot the baffle plate upwardly and to a condition somewhat parallel to the anticavitation plate. As the motor slows, the spring tension overcomes the thrust of the backwash to pivot the plate downwardly into the backwash to thereby slow forward motion of the boat. Since the torsion spring is utilized to apply a continuous force on the baffle plate, a serious amount of drag is produced to cut the operating efficiency of the attached motor throughout its full RPM range. This is very undesirable when the motor is being utilized for other than trolling purposes. The only locking mechanism provided with this apparatus is an abutment or projection that is formed integrally within the pivotable plate for engaging the anticavitation plate once the trolling plate reaches a downward position. The abutment surface functions to prevent the plate from pivoting into engagement with the propeller.
Another device similar to the Karasinski device is disclosed in U.S. Pat. No. 2,719,503 to D. D. Smith. Smith discloses a trolling plate attachment for outboard motors that is also continuously biased towards a downward position whereat the plate intersects the backwash created by the outboard motor propeller. Again, this device will reduce efficiency of the attached motor when it is operated at speeds faster than that required for trolling or moving extremely slow. In addition, Smith suggests the use of biasing springs of differing tension capacities in correspondence with the horsepower ratings of motors to be utilized therewith. An additional problem that is found when utilizing the spring biased type trolling plates is that when utilized with a motor having a reverse gear capability, little or no control in reverse operation may be had with a plate located in close proximity to the propeller. Experimentation has proven that an air cavity is formed between the plate and propeller when revese movement is attempted. Action of the propeller within the air cavity does not result in the production of a backwash in the desired direction in order to influence reverse directional movement of the boat.
It is a primary object of the present invention to provide a trolling device which incorporates a mechanical adjustment to allow a watercraft to come to a trolling speed without having to lower the idle RPM of the engine below the RPM specified by the manufacturer.
It is a further object to provide such a device that may be adapted to various horsepower inboard-outboard drive engines and outboard engines without necessitating replacement of mechanical parts of the device or the engines.
It is a yet further object to provide such a device that provides full maneuverability of the boat when operation in reverse.
A still further object is to provide such a device that will provide stabilizing action to the boat in all forward speeds and attitudes and, further, controls porpoising and skidding on turns.
An additional object is to provide such a device which allows full maneuverability during turns in all forward speeds.
A further object is to provide such a device that will enable operation by a single boat occupant from any position in the boat.
These and still further objects and advantages will become apparent upon reading the following disclosure, which, taken with the accompanying drawings, describe a preferred form of the present invention. It should be noted however that the drawings and following description are given only by way of example, the invention being defined solely by the appended claims.